Filtering queryset when working with Django is one of the most important and fun tasks to be done.
If you are familiar with working with array/list values, you might want to know how to optimize your queries when working with array fields or values. 🚀

Well, let's learn some filters methods or array fields or values.

The in() method for array values

Suppose that you have a list of ids. You want to filter a queryset to only have the entries with ids that match ids values in the list.

ids = [1,4,8,9]

Products.objects.filter(id__in=ids)

This is the equivalent in SQL:

SELECT * FROM products WHERE id IN (1,4,8,9);

The ArrayField

The ArrayField is a field used to store a list of data. We'll dive deeper into this field in another article. But here's a basic example of a model using this field.

from django.contrib.postgres.fields import ArrayField
from django.db import models

class Product(models.Model):
    name = models.CharField(max_length=255)
    tags = ArrayField(models.CharField(max_length=255), size=10)

Great! Let's say you want to retrieve from the database all products with the shoe tag, or even more interesting with the shoe and pants tags.

For this, you use the contains filter.

# Retrieving all products with shoe tag

Product.objects.filter(tags__contains=['shoe'])

# Retrieving all products with shoe and pant tags

Product.objects.filter(tags__contains=['shoe', 'pant'])

And that's it basically.👀

You can also find interesting filters such as contained_by which is the inverse of contains but also the overlap filter that checks that the retrieved entries contain at least a value with those passed.

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